Fuel cell technology has been identified as a potential alternative for the traditional internal-combustion engine conventionally used to power automobiles. It has been found that power cell plants are capable of achieving efficiencies as high as 55%, as compared to maximum efficiency of about 30% for internal combustion engines. Furthermore, fuel cell power plants produce zero tailpipe emissions and produce only heat and water as by-products.
Fuel cells include two basic components: an electrode and a Proton Exchange Membrane (PEM). Hydrogen fuel flows into one electrode which is coated with a catalyst that strips the hydrogen into electrons and protons. Protons pass through the PEM to the other electrode. Electrons cannot pass through the PEM and must travel through an external circuit, thereby producing electricity, which drives an electric motor that powers the automobile. Oxygen flows into the other electrode, where it combines with the hydrogen to produce water vapor, which is emitted from the tailpipe of the vehicle. Individual fuel cells can be stacked together in series to generate increasingly larger quantities of electricity.
While they are a promising development in automotive technology, fuel cells are characterized by a high operating temperature which presents a significant design challenge from the standpoint of maintaining the structural and operational integrity of the fuel cell stack. Maintaining the fuel cell stack within the temperature ranges that are required for optimum fuel cell operation depends on a highly-efficient cooling system which is suitable for the purpose.
Cooling systems for both the conventional internal combustion engine and the fuel cell system typically utilize a pump or pumps to circulate a coolant liquid through a network that is disposed in sufficient proximity to the system components to enable thermal exchange between the network and the components. Internal combustion engines use coolants that are high in electrical conductivity, typically having such constituents as water, ethylene glycol and additives such as corrosion inhibitors, pH adjustors and dyes. Fuel cell vehicles, in contrast, require a coolant which has a very low electrical conductivity since the coolant passes through the high-voltage fuel cell. Fuel cell vehicle coolants typically include a mixture of de-ionized water and ethylene glycol with no additives. The high conductivity which characterizes internal combustion engine coolants may cause short-circuiting if used in a fuel cell vehicle cooling system (FCVCS), leading to vehicle failure.
Due to the special low conductivity requirements of electric fuel cell vehicle cooling systems, a unique coolant having a low electrical conductivity is used in these systems. During circulation of the coolant throughout the fuel cell vehicle cooling system, however, ions are constantly leached from cooling system components such as plastic, metal and rubber hoses. Therefore, an ion-removing device is needed for removing ions from a coolant in a fuel cell vehicle cooling system in order to maintain low electrical conductivity of the coolant and prevent short-circuiting of the fuel cells which drive the vehicle.